Nikolay Kolev

Detection of SUSY in the stau-neutralino coannihilation region at the LHC

Abstract We study the feasibility of detecting the stau neutralino ( τ ˜ 1 – χ ˜ 1 0 ) coannihilation region at the LHC using tau (τ) leptons. The signal is characterized by multiple low energy τ leptons from χ ˜ 2 0 → τ τ ˜ 1 → τ τ χ ˜ 1 0 decays, where the τ ˜ 1 and χ ˜ 1 0 mass difference (ΔM) is constrained to be 5–15 GeV by current experimental bounds including the bound on the amount of neutralino cold dark matter. Within the framework of minimal supergravity models, we show that if hadronically decaying τs can be identified with 50% efficiency for visible p T > 20 GeV the observation of such signals is possible in the final state of two τ leptons plus large missing energy and two jets. With a gluino mass of 830 GeV the signal can be observed with as few as 3 – 10 fb −1 of data (depending on the size of ΔM). Using a mass measurement of the τ pairs with 10 fb −1 we can determine ΔM with a statistical uncertainty of 12% for Δ M = 10 GeV and an additional systematic uncertainty of 14% if the gluino mass has an uncertainty of 5%.

Bi-Event Subtraction Technique at Hadron Colliders

Abstract We propose the Bi-Event Subtraction Technique (BEST) as a method of modeling and subtracting large portions of the combinatoric background during reconstruction of particle decay chains at hadron colliders. The combinatoric background arises when it is impossible to know experimentally which observed particles come from the decay chain of interest. The background shape can be modeled by combining observed particles from different collision events and be subtracted away, greatly reducing the overall background. This idea has been demonstrated in various experiments in the past. We generalize it by showing how to apply BEST multiple times in a row to fully reconstruct a cascade decay. We show the power of BEST with two simulated examples of its application towards reconstruction of the top quark and a supersymmetric decay chain at the Large Hadron Collider.

Searching for top squarks at the LHC in fully hadronic final state

We pursue a scenario where the lighter top squark (stop) mass is accessible for the Large Hadron Collider (LHC) in the near future, while gluinos and first two generation squarks are heavier. At

Determination of Non-Universal Supergravity Models at the Large Hadron Collider

\sqrt{s} = 8

Cosmology and Dark Matter at the LHC

TeV, we investigate the identification of stops which decay predominantly into a top quark and the stable lightest supersymmetric particle. We use a simple kinematical variable,

Detection of SUSY Signals in Stau Neutralino Co‐annihilation Region at the LHC

M3

Top Squark Searches Using Dilepton Invariant Mass Distributions and Bino-Higgsino Dark Matter at the LHC

, to reconstruct two top quarks which are pair-produced from the stops, in the fully hadronic channel. The dominant Standard Model (SM) background for this signal stems from

Indirect measurements of the τ˜–χ˜10 mass difference and Mg˜ in the co-annihilation region of mSUGRA models at the LHC

t\bar t

Measurement of the Stau Minus Neutralino Mass Difference and Mgluino in the Co-Annihilation Region at the LHC

plus jets, with one top quark decaying into

Explaining the CMS dilepton mass endpoint in the NMSSM

bl\nu